I've got the exact same issue, Xcode launches my app three and sometimes 4 times. When this happens, the debugger does not work at all or maybe I'm using the wrong instance. The only way to fix it is to restart Xcode. So now every two minutes or so I need to restart. So yes, it does matter. Xcode is almost unusable these days. It's faster if I boot up a 10 year old machine and use Xcode on that.